Making 99 folders 99 folders deep Post: 302517085

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Top Forums Shell Programming and Scripting Making 99 folders 99 folders deep Post 302517085 by alister on Tuesday 26th of April 2011 03:28:21 AM

04-26-2011

Registered User

Perhaps something like the following:

Code:

#!/bin/sh

ndirs() (
    l=$l.
    if [ ${#l} -gt $n ]; then
        return 0
    fi
    cd "$1"
    for i in $(jot $n); do
         mkdir $i
         ndirs $i
    done
)

l=               # Current level
n=$1             # How many levels / How many dirs per level
d=${2:-$PWD}     # Starting directory

ndirs "$d"

This approach is not at all efficient. It constantly spawns subshells. But it is succinct since the changes to the current working directory are not seen by parent shells.

The script takes two arguments. The first is mandatory, the number of levels (which is also the number of directories per level). The second is optional, the starting point for directory creation (defaults to the current directory).

The jot can be replaced with seq or with some other facility that your shell may provide for creating a list from a range for the for-loop.

Also, in my earlier calculations, I underestimated the number of directories created. Yes. Those estimates were actually low. The number of directories is not n^n, but n + n^2 + n^3 + ... + n^n.

Regards,
Alister

Last edited by alister; 04-26-2011 at 04:44 AM..

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LEARN ABOUT OPENDARWIN

pwd

PWD(1)							    BSD General Commands Manual 						    PWD(1)

NAME

     pwd -- return working directory name

SYNOPSIS

     pwd [-LP]

DESCRIPTION

     The pwd utility writes the absolute pathname of the current working directory to the standard output.

     Some shells may provide a builtin pwd command which is similar or identical to this utility.  Consult the builtin(1) manual page.

     The options are as follows:

     -L      Display the logical current working directory.

     -P      Display the physical current working directory (all symbolic links resolved).

     If no options are specified, the -P option is assumed.

ENVIRONMENT

     Environment variables used by pwd:

     PWD  Logical current working directory.

DIAGNOSTICS

     The pwd utility exits 0 on success, and >0 if an error occurs.

STANDARDS

     The pwd utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

SEE ALSO

     builtin(1), cd(1), csh(1), sh(1), getcwd(3)

BUGS

     In csh(1) the command dirs is always faster because it is built into that shell.  However, it can give a different answer in the rare case
     that the current directory or a containing directory was moved after the shell descended into it.

     The -L option does not work unless the PWD environment variable is exported by the shell.

BSD
								 February 4, 2002							       BSD